During the normal running of a vehicle, the amount of carbon oxide in the discharged exhaust is small since the speed of the engine is relatively high. However, when the engine runs at an idle speed when the vehicle is stopped, exhaust containing a large amount of carbon oxide is discharged because of incomplete combustion of the fuel. Thus, if the engine is in the idle state when the vehicle is stopped while the air conditioner still runs, carbon oxide will be drawn into and gathered in the vehicle cabin gradually, so persons in the vehicle cabin may be poisoned unconsciously to loss awareness, or even loss life in serious conditions.
In order to avoid such carbon oxide poisoning, various in-vehicle carbon oxide sensing and warning solutions have been developed according to prior art. These solutions, however, are generally based on sensing the concentration of in-vehicle carbon oxide by using carbon oxide sensing devices, and a warning is sent out when the concentration of carbon oxide exceeds a certain level.
According to this type of prior art, carbon oxide sensing devices need to be added, which results in higher cost of the vehicle. In addition, the life time of carbon oxide sensing devices is short, for example, only about one or two years for a general carbon oxide sensor, so updating in-vehicle carbon oxide sensing devices is a nuisance; and, on the other hand, long life carbon oxide sensing devices are accompanied by higher cost.